Shane Kumpf created YARN-8035:
---------------------------------
Summary: Uncaught exception in ContainersMonitorImpl during
relaunch due to the process ID changing
Key: YARN-8035
URL: https://issues.apache.org/jira/browse/YARN-8035
Project: Hadoop YARN
Issue Type: Bug
Reporter: Shane Kumpf
In the case of a container relaunch event, the container ID is reused but a new
process is spawned. For resource monitoring, {{ContainersMonitorImpl}} will
obtain the new PID post relaunch and initialize the process tree monitoring. As
part of this initialization, a tag called {{ContainerPid}}, whose value is the
PID for the container, is populated for the metrics associated with the
container. If the prior container failed after its process started, the
original PID will already be populated for the container, resulting in the
{{MetricsException}} below.
{code:java}
2018-03-16 11:59:02,563 WARN
org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainersMonitorImpl:
Uncaught exception in ContainersMonitorImpl while monitoring resource of
container_1521201379995_0001_01_000002
org.apache.hadoop.metrics2.MetricsException: Tag ContainerPid already exists!
at
org.apache.hadoop.metrics2.lib.MetricsRegistry.checkTagName(MetricsRegistry.java:433)
at org.apache.hadoop.metrics2.lib.MetricsRegistry.tag(MetricsRegistry.java:394)
at org.apache.hadoop.metrics2.lib.MetricsRegistry.tag(MetricsRegistry.java:400)
at
org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainerMetrics.recordProcessId(ContainerMetrics.java:277)
at
org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainersMonitorImpl$MonitoringThread.initializeProcessTrees(ContainersMonitorImpl.java:559)
at
org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainersMonitorImpl$MonitoringThread.run(ContainersMonitorImpl.java:448){code}
{{MetricsRegistry}} provides a {{tag}} method that allows for updating the
value of an existing tag. Updating the value ensures that the PID associated
with container is the currently running process, which appears to be an
appropriate fix. However, it's unclear how this tag might be being used by
other systems. I'm not finding any usage in Hadoop itself.
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